Postretirement Benefits - Benefit Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Projected benefit obligation:
Projected benefit obligation, beginning of year	$ 1,013,767	$ 993,554
Service cost for benefits earned	35,471	34,554	$ 28,763
Interest cost on benefit obligation	58,748	52,688	50,193
Plan amendments	1,935	1,146
Actuarial loss (gain)	36,300	(28,250)
Benefits paid	(39,887)	(35,924)
Settlements	(3,252)	(4,001)
Projected benefit obligation, end of year	1,103,082	1,013,767	$ 993,554
Accumulated benefit obligation, end of year	935,049	$ 860,855
Employee Pension Plan
Projected benefit obligation:
Projected benefit obligations increase	$ 89,300
Discount rate	5.72%	5.87%